Treasury figures provided to a Senate estimates committee showed in 2017, the largest spending component for immigration and border protection activities was onshore compliance and detention, followed by $1.083 billion for the management of irregular boat arrivals and $1.059 billion on border enforcement.

A further $242 million was spent by authorities on border management efforts around Australia while $109 million went to cooperation arrangements with other countries across the region.

The figures follow a near $5 billion price tag for five years of Australia's offshore immigration detention program, including the total operational and infrastructure costs for Australia's detention facilities on Nauru and Papua New Guinea's Manus Island, peaking in 2015-16.

"Notwithstanding the success of Australia's strong border protection policies in stopping illegal maritime arrivals to Australia, the government continues to manage persons who arrived illegally by boat in 2012 and 2013; both through offshore and onshore arrangements," Treasury officials told Parliament.

The latest round of resettlements for individual detainees is expected in the first part of 2018.

In 2016, a report by Save the Children and UNICEF found taxpayers had spent as much as $9.6 billion on offshore immigration enforcement since 2013, while research by the Parliamentary Library study found Manus Island had cost taxpayers about $2 billion since it was reopened by the Gillard government in late 2012.

That cost equalled more than $1 million for each of the 2000 people who had been held on the island.

The latest figures from the newly established Home Affairs Department show 1300 people were being held in immigration detention at the end of 2017, including 265 on Nauru.

A total of 988 people were in immigration detention on the mainland and 313 were being held on Christmas Island.

New Zealand nationals remained the largest group in detention at 13.5 per cent, followed by those from Sri Lanka at 7.8 per cent, Vietnam at 7.6 per cent, Iran at 6.8 per cent and China at 5.7 per cent.